Question

What happens when dilute hydrochloric acid is added to iron fillings?
(a).Hydrogen gas and iron chloride are produced
(b).Chlorine gas and iron hydroxide are produced
(c).No reaction takes place
(d).iron salt and water are produced

Answer 1

Hint: In a chemical reaction, when one or more elements replace one or more elements in a compound, the reaction is called a single displacement reaction. When HCl is added to iron fillings such a displacement occurs.

Complete answer:
When we study metals, we learn about its reaction with acids. Metals can displace hydrogen from an acid and form a salt and release hydrogen gas. It does not give salt and water like the reaction between acid and a base. Therefore, when dilute hydrochloric acid reacts with iron filling, the salt iron(II) chloride and hydrogen gas is produced. The reaction is shown as follows
\[Fe+2HCl\to FeC{{l}_{2}}+{{H}_{2}}\]

Hence, Iron fillings react with dilute hydrochloric acid to give hydrogen gas and iron chloride are produced and the correct answer is option (a).

Additional Information:
A single displacement reaction is represented as
\[A+B-C\to A-C+B\]
Here A is more reactive than B, and C represents an anion or could be any halogen. In this reaction C is spectator ion, when AC and BC are aqueous compounds. Sometimes, displacement reactions can also act as redox reactions. Here are two types of such reaction, cation replacement reaction and anion replacement reaction. In cation replacement reactions, cation is replaced and is reduced whereas in anion replacement reaction an element in its reduced form is converted to its anion.

Note: Not all metals can displace hydrogen from an acid, when the metal reacts with acid. Only those metals which are above hydrogen in the activity series can undergo a single displacement reaction with an acid to give hydrogen gas.